Friday, May 1, 2009

Scientists put carbon ceiling at a trillion tonnes


Scientists hope a new approach to assessing carbon build-up in the atmosphere will simplify issues for policymakers and economists.

Two papers published in Nature  show that the timings of carbon emissions are not relevant to the debate — it is the total amount of carbon dioxide emitted over hundreds of years that is the key issue. 

Rather than basing negotiations on short-term goals such as emission rates by a given year, the researchers say the atmosphere can be regarded as a tank of finite size which we must not overfill if we want to avoid a dangerous temperature rise. 

Climate policy has traditionally concentrated on cutting emission rates by a given year, such as 2020 or 2050, without placing these goals within the overall context of needing to limit cumulative emissions.

Both papers analyse how the world can keep the rise in average surface temperatures down to no more than two degrees Celsius above pre-industrial levels. This figure is widely regarded as the threshold beyond which the risk of dangerous climate change rapidly increases. Policymakers around the world have adopted this limit as a goal.

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